The Myth ... of the Myth of Junk DNA

Some interesting items this week in the science blogosphere related to Junk DNA. As University of Toronto biochemist Larry Moran points out, ID proponents are gearing up to tout a new book claiming Junk DNA is a myth--and that the human genome is filled with intelligently designed genes with functions scientists are only now beginning to understand.

Key to the "myth" talking points of creationists is the notion that when biologists back in the 1970s first began realizing how large a percentage of the human genome was non-coding, they simply asserted it was functionless 'junk' in line with their innate Darwinian bias. And now, suddenly, to their utter surprise and chagrin, various functions are in fact being discovered for the junk.

From which we are to conclude, the creationist argument goes, that most scientists are knee-jerk ideological Darwinists, and isn't this another good reason to get a better theory like intelligent design into the public school science classrooms.

T. Ryan Gregory at Genomicron has tirelessly pointed out the problems with the myth argument over the past few years. He cites a number of articles from the journals of the time to show that scientists never dismissed junk DNA in the literature. His blog is a great resource on the subject in general.

Many mutations are neutral, or can be easily overcome by technology. And some of them cause a great deal of psychological suffering, such as the mutation that causes trimethylaminuria, which is physically harmless but causes the victims to smell like rotten fish no matter how clean they are. But many other mutations are deadly or, worse yet, can cause a person to have a lifetime of suffering. Perhaps the most disturbing mutation is the one that causes Lesch-Nyhan syndrome. This one mutation, of a single amino acid in a protein, causes the victim to have an uncontrollable compulsion for self-mutilation: they chew their own lips and fingers, and find sharp objects to stab their faces and eyes. The victims are fully able to feel their pain and they know what they are doing, but cannot control it.

Obviously to argue such mutations are the product of intentional design is to suggest the deity or intelligence responsible, is something of a monster. But it's even more problematic, Rice argues: the very structure of the genome itself --not just the mutations--is inconsistent with the idea that the genome, or the human body, or the world was directly designed by an external agent.

The human genome is full of stuff that interferes with the use of genetic information to produce healthy and functional enzymes and bodies. First, consider the fact that only about 1 percent of human DNA codes for those enzymes. About 68 percent of the DNA consists of non-coding DNA that is between the genes, and about 31 percent of the DNA consists of non-coding DNA that is inside of the genes. This is, at best, a clumsy system, because whenever a cell divides, all of this DNA is copied, not just the DNA that the cell will use. In addition, since each gene is broken into little “exon” fragments by a large amount of internal “intron” DNA, the genetic information must be spliced together in order to be put to use. That is, to get a functional enzyme, the genetic information from lots of exon fragments has to be cobbled together. If it works, there is no problem, but the whole system is so cumbersomely complex that it often fails. Not only are many genetic diseases caused by mutations in the genes themselves, but many genetic diseases are caused by (or also caused by) failures of the cell to deal properly with the non-coding DNA and the splicing.

Avise's book is excellent, although other scientists have not found it free of its own problems when it comes to the topic of theodicy.

Image via Wikipedia

UPDATE: 5.24.11 At the Discovery Institute's site, Casey Luskin is apparently claiming this post was a review of their new book. "John Farrell has written a critique of Jonathan Wells' new book The Myth of Junk DNA. The only problem is that many of the arguments Farrell critiques aren't ones that Jonathan Wells makes in the book."

The only problem is, the post is about other science bloggers discussing the topic in light of the book's release. In the comments, I invited Casey to send me a copy of the book to review, but as yet he has not responded.